There, in southern Spain on Monday, the 2008 world champion got his first ever taste of a Formula One car other than a McLaren.

It was, however, only a pre-test filming day on promotional Pirelli tyres, and at one point Hamilton ran out of fuel and had to return to the pits.

He is not expecting the new 'vanity-panelled' W04 to be an early winner, but he is already pushing for changes.

"The steering wheel has twice as many buttons as last year and I've already got rid of some," said Hamilton.

Some have scoffed at his decision to jump ship from almost race-winning certainty at McLaren bound for Mercedes, an outfit with apparent turmoil in the ranks of upper management and having won just a single Grand Prix in three years.

As for the critics, Hamilton insisted: "Everyone has got an opinion but I think they should just keep it to themselves.

"It is my decision; it is nothing to do with any of these people who are commenting on it. I feel good about it and that is all that matters."

Also feeling good on Monday was Nico Rosberg, who is well placed to give early comments on the W04, having been Michael Schumacher's teammate at the Brackley based team since 2010.

"Wow, it immediately felt right -- no problems at all," said the German.

"This was not the case in recent years."

Team boss Ross Brawn also felt moved to defend the new silver single seater, following initial reports that it features almost no innovation.

"Some probably need to take a closer look," he said.

"There's a lot of innovation under the skin which I'm pleased about," added Brawn, revealing that a "very interesting new front wing" will be tested on Tuesday.

Some reports, however, said that while Red Bull and particularly Sauber are pushing the boundaries with ultra-slim sidepods, Mercedes may even have taken a backwards step.

"The looks are deceptive," Brawn is quoted by Auto Motor und Sport. "Our sidepods have been reduced in width, but maybe not as much as Sauber," he smiled.